The invention relates to a mounting of the bottom bearing ring of a rotating deck or a superstructure of a crane on a mast. Said mounting comprises bearing slides, which are spaced apart and connected to the inside of the bearing ring and which support the bearing bodies, which are made of a high quality sliding material and are braced against an annular peripheral surface of the mast. Such mast-type cranes can be mounted on trucks, but are used preferably as offshore cranes. xe2x80x9cIn U.S. Pat. No. 5,310,067 such a pedestal crane having upperworks and boom means and a self-adjusting bearing means disposed between the upperworks and pedestal means is described. This known crane comprises means for removably securing the bearing means within that upperworks against vertical displacement, means for removably securing said bearing means against circumferential displacement, means for permitting within limits the automatic translation of that bearing means in a generally horizontal plane under load and means for permitting within limits the automatic angular rotation of said bearing means in a generally vertical plane under load, whereby the bearing means may automatically and controllably compensate for the angular misalignment between the longitudinal axis of said pedestal means and the axis of rotation of said upperworks and boom means.xe2x80x9d In this prior art the base plate of the rotating deck is provided with a circular cutout, hole, which is adapted to the diameter of the xe2x80x9ccentral postxe2x80x9d, forming the xe2x80x9cpedestal meansxe2x80x9d, and whose periphery is provided with recesses, into which the xe2x80x9cbacking membersxe2x80x9d, forming the bearing slides, are installed in a manner that they can move relative to the xe2x80x9cbase platexe2x80x9d in a horizontal plane and, in particular, can rotate about a horizontal axis, when a load, hanging on the xe2x80x9cboomxe2x80x9d, xe2x80x9cis exerted on the upperworks and the base platexe2x80x9d.
However, such an ability to deform the xe2x80x9cbearing means in relation to the base platexe2x80x9d is undesired for various reason. First of all, the radial displacement of the bearing slides in relation to the bearing ring of the rotating deck is a problem. This horizontal displacement of the bearings takes place when the load is affixed for the first time and thereafter never resets itself. This means that the position of the bearings remains constant, that is pushed back, in the radial direction, since there are no resetting forces after unloading. Thus, the entire mounting exhibits slack. In addition, the bearing slides, which are pushed back, do not become active again until correspondingly large forces act on the crane.
Secondly, the rotation of the bearing slides about the horizontal axis is a problem. According to the U.S. Pat. No. 5,310,067, the rotation about the said horizontal axis is accomplished by means of a deformation of the bearing slides. xe2x80x9cParticularly, the rather thin retainer member is bent so as to permit the subassembly including the backing member and the wear material to rotate about its support about an axis perpendicular to the load direction.xe2x80x9d This rotation of the xe2x80x9cretainer memberxe2x80x9d can lead to resilient deformations. In any case the service life is significantly reduced as a consequence of the increasing stress and the subsequent back and forth deformation of the bearing slides.
Therefore, the object of the invention is to provide a mounting of the prior art type that prevents the xe2x80x9cbearing meansxe2x80x9d from sloping in relation to the bottom bearing ring of the rotating deck.
The invention solves this problem in that each bearing slide comprises a steel plate with a flat rearside, whose entire area rests without tilting against a flat support surface of the bearing ring, and that the bearing slide is connected to the ring so as not to rotate or move. In the inventive mounting, a flexible movement of the bearing slide in relation to the bottom bearing ring, supporting the rotating deck, is ruled out so that the xe2x80x9cbearing meansxe2x80x9d remain undeformed even under load.
Of course, the bearing slides can be interchanged with the bearing bodies in order to prevent wear exceeding the allowable amount.
A preferred embodiment provides that the rearside of the plate is welded in the shape of a yoke to two pairs of brackets, which stand at right angles on said rearside and which enclose the faces of the ring. Furthermore, the brackets and the ring are provided with aligned boreholes, through which are guided the connecting screws. Owing to this type of screw connection of the plate with the bearing ring, said bearing ring cannot tilt when resting against the support surface of the bearing ring.
Another preferred embodiment provides that the rearside of the plate is welded in the area of the upper edge to two brackets, which stand vertically on said rearside. The plate is provided with ear-shaped continuations, which project beyond the bottom edge. Angular pieces are screwed to the continuations; and the brackets and the upper legs of the angular pieces envelop the faces of the bearing ring. The connecting screws are guided through the aligned boreholes of the brackets, the bearing ring and the upper legs of the angular pieces. This embodiment of the invention permits the rotating deck of the crane to be put, first of all, without the bearing slides on the mast and to insert the bearing slides from the top between the mast and the bearing ring at a later point in time. With the bearing slides removed and the corresponding existing slack, it is much easier, or optionally it permits now, the rotating deck to be mounted on the mast. Similarly there is also the option of disassembling again the bearing slides later.
Another embodiment provides that the plates are provided on the edges, projecting beyond the side continuations or the faces of the bearing rings, with boreholes, which align with the boreholes of the bases, fastened to the faces of the bearing ring, and that connecting screws are guided through the aligned boreholes. These connecting screws can be continuous tightening screws. The boreholes in the bases, welded to the bearing ring, can also be threaded boreholes, into which the connecting screws are then screwed.
The plates can be recessed into recesses of the bearing ring that correspond to the length of said plates so that said plates are fixed in position in the recesses so that they cannot rotate in the circumferential direction.
The narrow sides of the plates can be provided with yoke-like continuations, which engage with the approximately radial, step-shaped sides of the recesses and form additional protection against tilting and axial displacement.
Only the upper regions of the narrow sides of the plates can also be provided with a continuation, which engages with the step-shaped sides and which permits then, after disconnecting the screws, the plates to be pulled out in the direction of the top or, in particular, permits the bearing slides to be inserted later from the top.
The front sides of the plates are provided with retaining members for the purpose of fastening the bearing bodies.
In a further development of the invention the bearing slides and the bearing ring are designed in such a manner that the force is always introduced over the support surface of the bearing ring, thus without generating in essence any moments. The axial projecting length of the bearing body, made of a sliding material, in the longitudinal direction of the mast beyond the support surface of the bearing ring is very small. Thus, radial forces, acting on the upper and bottom edges of the bearing bodies, cannot exert any large tilt moments. The entire area of the bearing slides is braced and the forces are passed uniformly into the bearing ring. Preferably the bearing body in the axial direction is at a maximum one third thicker than the bearing ring.
Even with the use of soft sliding material for the bearing bodies, the wear and friction on the opposing surfaces cannot be avoided. In order not to weaken the mast, there is preferably a ring, which is welded on the mast and is subject to the action of the bearing slides. Thus, even if the bearing bodies grind in or cause wear of the counter-surface, the material of the mast remains unaffected. Notch effects or a weakening of the mast cannot occur, since the material of the mast itself does not form the sliding surface for the bearing slides.
Since the mounting of the bearing slides on the bearing ring cannot be displaced, rotated or tilted, it is possible for the bearing bodies, made of sliding material, to wear nonuniformly. However, they are parts subject to wear and hence are readily interchangeable. However, the significant advantage of the inventive mounting lies in the fact that there are no problems associated with the service life. The bearing slides are no longer subject to alternating bending, which leads to premature fatigue. In addition, a weakening of the mast is ruled out. Finally there is no bearing slack due to the remaining deformation of the mounting.